Expression control for electrical musical instruments.



M. L. SEVERY & G. B. SINCLAIR.

EXPRESSION CONTROL FOR ELECTRICAL MUSICAL INSTRUMENTS.

APPLICATION FILED JUNE 26, 1907- 1,183,244;

2 SHEETSSHEET 1- Figrl In'venfiW f, fifdvin L. Severy, George S indair;

' Patented May16, 1916.

flftarng M. L. SEVERY & G. B. SINCLAIR. EXPRESSION CONTROL FORELECTRICAL MUSICAL INSTRUMENTS. APPLICATION FILED JUNE 26.1907.1,183,244. Patented- May16, 1916.

2 SHEETS-SHEET 2.

flfl' 63 I Im/m LETJ,

2 W fiwz I LTeIviI LL. Severy,

UNITED sTATEs PATENT OFFICE.

MELVIN L. SEVERY, OF ARLINGTON HEIGHTS, AND GEORGE B. SIN CLAIR, OFMELDFORID,

' MASSACHUSETTS, ASSIGNORS TO CHORALGELO COMPANY, OF BOSTON, MASSACHU-SETTS, A CORPORATION OF MAINE.

EXPRESSION CONTROL FOR ELECTRICAL MUSICAL INSTRUMENTS.

Specification of Letters Patent.

Application filed June 26, 1907. Serial No. 380,987.

To all whom it may concern Be it known that we, MELVIN L. SEVERY, ofArlington Heights, county of Middlesex, and Commonwealth ofMassachusetts, and GEORGE B. SINCLAIR, of Medford, county of Middlesex,and said Commonwealth, both citizens of the United States, have made certain new and useful Improvements in EX- pression Control for ElectricalMusical Intruments, of which the following is a specification.

This invention pertains to that class of musical. instruments whereinmagnetically attractive sonorous bodies are vibrated by means ofelectromagnets having properly timed electric pulsations deliveredthereto;

and the object of our invention is the construction of means forcontrolling the volume and loudness of the music produced by theinstrument. We set forth in this case a type of our invention in whichthe sonorous bodies are metallic strings of the kind usually employed inmusical instruments.

One of the essential features of our invention comprises a permanentindividual loudness control operating to voice the individual tones ofthe musical gamut, and consisting of specially wound electromagnets forthe actuation of the strings, so adapted that the attractive energy ofeach magnet is proportioned to the peculiar conditions of its associatedstring or strings, to the end that the instrument shall be correctlyvoiced. I

Another feature of our invention consists in changing at will thevoltage of the current which energizes the electromagnets, and therebyvarying the amplitude of vibration of their associated strings.

In certain co-pending applications we have shown, described and claimedfeatures which are illustrated and described in the tions we havebroadly claimed the art of producing musical tones, which art isinvolvedbut is not claimed in the fpresent application. All matters setforth-an'd claimed in co-pending: applications filed in our names, or inthe names of either of us, and not specifically claimed herein, areexpressly saved and reserved for one or another :of such applications.Among these may be generator 40.

noted our joint applications Serial No.

Patented May 16, 1916- 273,199, filed August 7, 1905; Serial No.377,571, filed June 6, 1907; Serial No. 379,714, filed June 19, .1907;Serial No.

537,257, filed January 10, 1910; Serial No. 740,201, filed January 4,1913; Serial No. 753,013, filed March 8, 1913; and Serial No. 7 54,47 5,filed March 15, 191-3.

Referring to the drawings forming part of this specification, Figure 1is a perspective digrammatic view of a musical instrument embodying ourinvention. Fig. 2 is a detail plan view of the magnet rail and itsadjusting devices. Fig. 3 is a diagram illustrative of the pedaloperated octave coupler, and of certain types of variable resistancesused in connection with the instrument.

The sonorous bodies, which are shown in the drawings as magneticallyattractive strlngs 1, are vibrated by means of electromagnets 10, towhich properly timed electric pulsations are delivered upon thedepression of the keys 3. The means for producing the properly timedpulsations consists of a source of electric current, and make-andbreakdevices comprising uniformly rotated toothed disks 12 and brushes l3contacting therewith.

The circuit between the generator 40 shown in Fig. 1, and theelectromagnets 10 comprises the wire 16, brush 14, shaft 11, disks 12,brushes 13, and wires 39; the return from said electromagnets 10embracing the wires 26, contacts 25, brushes 24 of such keys as aredepressed, Wire 59, (where the keys depressed are treble ones), brush96, contact 97 (where the octave coupler bar 90 is in the position shownin Fig. 1)' wire 100,

brush 53, contact 51, wire 62, resistance 60, wire 61 to the properarmature brush of the The return circuit for the bass electromagnetswill embrace wires 26, contacts 25, brushes 24, wire 58, brush 55,contact 50, wire 52, contact 51, wire 62, resistance 60, and wire 61back to said armaturebrush. If, now, a key 3 is slightly depressed, itsbrush 24 will be put into touch with a contact 25,-and the current .willtraverse the resistances 28,28 and the short connecting wires 29, 29 tothe wire 26, and thence to the electromagnet associated with the same.This gives a greater resistance to the current than is received whensaid brush is raised into touch with the contact 25 and hence only oneresistance 28* is traversed; while the elevation of the brush to thecontact 25 short circuits all such resistances, and gives the fullstrength of actuating current to the electromagnet associated therewith.If desired, additional contacts and resistances may be employed, andthus give a still finer degree of differences. This gives the player acontrol approximating as closely as may be desired to that of theordinary piano, as far as delicacy of touch is concerned.

Our first-mentioned loudness-control is produced by winding theelectromagnets 10 in accordance with our discovery that the resistanceof such windings should be inversely proportional to the frequency ofthe vibrations. The theory underlying this is that the 7 more rapidly astring vibrates,reaching for the upper notes about two thousand persecond-, the more the self-induction of the windings and the magneticlag of the iron core of such electromagnet will interfere with the fiowof the current, and conse quently the less strongly the magnet will beactuated. In other words, the amount of current which will flow throughan electromagnetwhen the current is continuous, will be far greater thanthe amount which will flow when the current is rapidly interrupted; thestrength ofthe magnets attraction being found to diminish asthe rapidityof interruption is increased. Hence to producetheoretical uniformity inmagnetic attraction on the part of all the electromagnets of the gamut,such electromagnets should be wound with wire of diminished resistanceas the scale is ascended. In some cases we find it sufiicientlysatisfactory to use the same size of windings for severalelectromagnets; the heaviest sizes of wire being for the upper treblemagnets, the finest being for the low bass, and the intermediate magnetshaving windings of medium sized wires; although we show in the drawingsonly three such groups of windings, it is evident that any desirednumber may be used. Further, owing to the amplitude of the bass stringsvibrations and their consequent liability of striking theirelectromagnets, such electromagnets must be adapted for a strength ofattraction which will permit them to be located at a greater dis tancefrom the strings; one suificient to avoid the danger of such strikingwhile at the same time properly actuating the strings. By thusconstructing the electromagnets associated with the different strings sothat the attractive force of each magnet shall be proportioned to thepeculiar conditions of its string, we make an important advance in theproper voicing of the instrument.

Another method of voicing the strings consists in so proportioning thedistance of the electromagnets 10 from their respective strings that allthe latter shall be actuated with equal sonorous effect. Economy wouldnaturally suggest locating the magnets as near as possible to theirstrings, but other conditions determine how near they can be placed. Theupper treble strings being of limited vibrational excursion, can havetheir electromagnets located close thereto without danger of contact. Atthe same time, because of their slight mass and high tension, theirmagnets must be very close thereto in order to properly actuate them. Onthe other hand, the low bass strings, because of their large mass andinertia, need to have their electromagnets located as near to them as isconsistent with the danger of contact above referred to; but of coursenot so near as are the upper strings to their magnets. Moreover, theupper strings act so slightly upon the sounding board of the instrumentthat they must be more energetically vi,- brated than are the others;thus still more needing closeness of proximity between them and theirmagnets; while the low bass strings by their superior mass or weight,and a consequently more vigorous vibration of the sounding board, do notrequire to be as close to their magnets as do the upper strings. Theintermediate strings,

sion than the highest strings, and their consequent easier actuation,taken in connection with the increased effective current-action owing totheir less rapid current-interruption, need to have their electromagnetslocated farther away from them in order to maintain substantial equalityin sonorous effect with the strings both above and below them. Thisfeature of our invention is illustrated'by Fig. 2 which shows theelectromagnets at the right hand end of the magnet rail to be locatedmuch closer ,to their strings 1 than are the electromagnets at theextreme left hand, or bass end; while the electromagnets in the vicinityof the point 71 on said rail, are farther away from their strings 1 thanare the bass magnets. Said point of maximum distance we find to be aboutone third up from said bass end.

. While the electromagnets may be permanently fixed in their positionsrelative to their strings, we prefer to have them capable of movement atwill toward and from the latter in order to provide the player withanother means for varying the loudness of music produced. This can onlybe done, however, by some means which will move the intermediate magnetsmore than the others, and the most practical way in which this can beaccomplishedns by jointing the magnet rail at the point 71,"and alsohinging the ends of the same'at 75 and 76, and adapting the rail to beangularly moved by devices under the control of the player. This is mostimportant, for, were the magnet-rail to be moved through a series ofpositions each parallel with the other, a movement sufficient to affectan upper treble string would give no, appreciable alteration to others;and a movement away from the strings sufficient to reduce slightly thestrength of vibration of the intermediate strings, would be enough torender the upper treble strings or even the low bass strings practicallymute. Moreover, other natural laws come in play which must be consideredin adjusting the magnet-rail. In the first place the upper treblestrings are so fine and so close to their electromagnets that they donot appreciably come under the law of inverse squares, but mainly underthat of the magnetic shell, the strength of attraction varying almostdirectly as the distance. Consequently, the upper electromagnets can begiven a greater range of adjustment than would be the case under the lawof inverse squares; but the electromagnets being normally very close totheir strings, such adjustment must be slight.

The intermediate electromagnets, owing to the greater mass of thestrings and their distancefrom them, act mainly under the usual law ofinverse squares; and the bass electromagnets being slightly nearer theirstrings than are the intermediate ones, but not so close as the upperelectromagnets, act under a different combination or permutation of thetwo laws. It is therefore an evidently difficult task to shift themagnetrail at will, and still accurately preserve the relative sonorouseffects upon all the strings of the scale. To this end, several detailsare essential; that the pivotal point 75 of the treble end of themagnet-rail" be not too far from the upper-most string; that the pivotalpoint 76 be preferably much nearer the lowest string than the higheststring, and that the juncture 71 be adjusted toward and from the stringsby a pedal, knee-swell or other device adapted to move said juncture sothat equal increments or decrements of the pedal will produce equalincrements or decrements of sonorous effect. We have discovered thatwhenever a direct current is broken it becomes practically like analternating current, and it offers an immensely greater lmpedance as thebreaks become fasing current. On account of the many factors alreadyreferred to it is necessary, in order to produce these results, thatequal movements of the pedal shall produce unequal and shifting degreesof motion of the rail. To accomplish the last requirement, theknee-swell 78 is provided With a cam or suitably plotted Wedge 77engaging a rod 74 connected with the lever 72 pivotally supported at 73and having its short arm joined to said juncture; such wedge or cambeing so proportioned that a uniform movement imparted to the pedal 78will cause a similarly uniform variation in the sound produced.

Another method of expression control, that of changing at will theVoltage of the magnet-energizing current, is accomplished by suitablyaltering the strength of excitercurrent, delivered to the field windingsof i the generator 40. To do this we preferably but not necessarily havethe exciter current entirely outside the armature circuit, and introduceinto the same a resistance cut in and out by a suitable pedal. Theimportant feature is to provide any means of increasing and diminishingcurrent in the field of the generator, whether external or not. Thegenerator field windings 41 are joined by a wire 42 to one pole of thecurrent source 43, and by a wire 48 to the brush 46 movable byapedal 47along a resistance 45 which is joined by a wire 44 to the opposite. poleof said current-source. When said pedal is in its elevated position, itsbrush is in contact with the lower end of said resistance, and sointroduces a maximum resistance into the circuit and allows a mimimumcurrent to pass to the field magnets. This causes a current of lowestvoltage to be generated by the generator 40, and thereby supplies to theelectromagnets 10 a minimum intensity of energy. As said pedal 47 isdepressed, successive increments of resistance are cut out, with acorresponding increase in excitercurrent, in voltage of currentgenerated, an

in strength of sound evolved.

Another method of control, that by which I we preserve a proper sonorousbalance be tween the various parts of the instrument, is needed in orderto overcome the tendency which we have discovered of the bass notesbeing overbalanced by the treble notes when increased current isdelivered to their actuating magnets 10. The means by which we correctthis consists of a rheostat 60 adapted to be switched into theenergizing circuits to the bass and treble strings by means of asuitable|pedal=56, with a'constantly larger amount of-resistance in thetreble circuit than in the bass circuit." 111 doing this, the pedal 56.is operatively'connected with a swmging arm 57 carryingbrushes 53, 54,55 in touch with the two sets of contacts 51, 50. Each of the contacts51 arm 57 said brush 53 will sweep over more of the contacts 51 for thesame angular movement of said arm, than does the brush 55 over itscontacts, with the result that after the arm 57 has been moved to anydegree the brush 53 will be in touch with the contact 51 connected witha greater resistance 60 than will be the brush 55. Such dissimilarity incurrents we find to be suflicient to equalize the two section's of theinstrum'ent, and render them equal in expression however much suchexpression is varied in the instrument as a whole.

In our method which pertains to means for preventing the abruptness oftransition from one number to another number of strings simultaneouslysounded, our purpose is to out less resistance into the treble circuitwhen the octave coupler is operated, than when it is not used; the basscircuit being unchanged. For we have discovered that although the tonesproduced by a few simultaneously energized the brush 54 being shorterthan the brush 55, more resistancewill be switched into the treblecircuit than the bass circuit, in the same way as is done by the twobrushes 53 and 55. But it will be noted that less resistance is cut intothe treble circuit by the brush 54, than is put into the same circuit bythe brush 53 when the coupler bar 90 is in its normal elevated position.Hence whenever the coupler bar 90 is depressed a lesser resistance willbe cut into the treble circuit than when it is not depressed, throughthe above. described arrangement; and the coupled magnets will be causedtoreceive sufficient additional current to make up for the loss ofenergy due to',subdivision among the several magnets. When the couplerbar is thus depressed the circuit will include wire 61, topmost wire 62,contact 51, wire 52, contact 50, brush 54,

wire 99, contact 98, brush 96, wire 59 to the brushes 24.

v electromagnets will not be materially weaker than the tone produced bya single electromagnet which Another method of varying the loudness ofthe instrument is illustrated in Fig. 3, and consists in theintroduction of a resistance into the circuit of each electromagnet 10of the entire gamut, and the provision of a pedal 83 adapted for cuttingin and out suitably proportional degrees of all such resistancessimultaneously. As shown, the resistances 80 are each connected by awire 39 to the electromagnets 10, While brushes 81 are joined by wires84 to the appropriate make-and-break brushes l3. Said brushes 81 arecarried by a bar 82 which is moved by said pedal 83, so that when saidbar rises through the depression of said pedal all the brushes 81 aremade to cutout the proper amounts of resistance and increase thestrength of the currents delivered to the electromagnets; therebyincreasing and properly modulating the music produced. This is what weterm our individual pedal rheostat, and it serves to enable the loudnessto be varied in sensibly equal amount for each string, independently ofwhether one or several strings are simultaneously sounded. A furtherexpression control is also illustrated in Fig. 3, and is one wherein apedal 87 cuts in or out at will a resistance to the common part of thecircuits of all the electromagnets. The resistance 85 shown here isconnected at one extremity to the key brushes 24-by means of a wire 88,while said pedal is provided with a brush 86 and is itself connected bya wire 89 to the current source 15. By depressing said pedal, said brushis elevated and made to cut out successive increments of. resistance,and thereby to increase the strength of the sound produced. Stillanother method of expression is obtained by the introduction of aresistance 95 into each of the coupling wires 94 of certain of thecoupler brushes 93. Through this arrangement the coupled magnets 10 onthe side of the resistance opposite that on which the keys are depressedwill be less strongly energized than the mag nets upon the same side asthe depressed keys; and either the lower strings can be made topredominate over the upper strings,

or the upper over the lower, by playing upon the keys associated withthe strings desired to thus predominate.

Another exceedingly important element of our musical instrument is thatby means of which the electric pulsations delivered to theelectromagnets 10 shall be timed with absolute accuracy. The slightestdegree less than this renders the instrument a failure as a musicalinstrument. A variation of one ten-thousandth of a second in therotation of the make-and-break disks 12, cannot be allowed. Accordingly,a governing device for said disks which can control the same with anaccuracy heretofore undreamed of, is not simply desirable, but isabsolutely essential. After years of experimentation, we produced such agovernor and applied the same to our electrical musical instruments,with the result of converting them into an unqualified success, whereall others were failures. Such a governor is indicated at 111 in Fig. 1of the drawings forming part of this specification, as controlling andtiming the rotation of the disks 12.

Although we have described our invention as applied toelectromagnetically actuated strings, we do not restrict ourselvesthereto, as other types of sonorous bodies with the respective bodiesfor effecting their may be employed.

What we claim as our invention and for which we desire Letters Patent isas follows, to wit v 1. An electric musical instrument having sonorousbodies of different pitch, electromagnets for their actuation, a sourceof current, currentpulsating means, and circuits including said source,electromagnets and pulsating means, the circuits associated withsonorous bodies of lower relative pitch be ing given materially greaterresistance than the circuits associated with bodies of higher pitch.

2. An electric musical instrument havin sonorous bodies of differentpitch, electromagnets for their actuation, a source of current,current-pulsatingmeans, and circuits including said source,electromagnets and pulsating means, the electromagnets associated withsonorous bodies'of higher rela tive pitch being given less resistancethan the electromagnets associated with bodies of lower pitch.

3. An electrical musical instrument comprising, in combination, sonorousbodies ,of different pitch; electromagnets associated vibration; andmeans for supplying the coils of the respective magnets with pulsationsof electric energy differing in frequency for the different magnets, thewindings of different magnets offering predce termined resistancedifiering in degree to compensate for varying impedance ofiered bysaid'windings incident to varying frequency of pulsation of currenttherein.

4. A musical instrument comprising magnetically attractive sonorousbodies, electromagnets to which said bodies respectively bear therelation of armatures, and means, including circuits and a source ofelectrical power, for delivering properly-timed elec-. tric pulsationsto said electromagnets; said electromagnets being located at differingdistances from their sonorous bodies, and including in their circuitsresistances which vary inversely proportional to the frequency of saidpulsations. 5. A musical instrument comprising tuned sonorous bodies,electrO-magnets for their sonorous bodies, electro-magnets for theiractuation, means for delivering properlytimed electric pulsations .tosaid electromagnets, a source of power, and circuits in cluding saidsource and electromagnets; said circuits having different ohmicresistances, said resistances increasing from the treble magnets to thebass magnets.

7. A musical instrument comprising tuned sonorous bodies,electro-magnets for their actuation, and means for delivering properlytimed electric pulsations to said electromagnets; the electromagnetsactuating upper sonorous bodies being wound with heavier wire than theelectromagnets of the sonorous bodies lower in thescale.

8. A musical instrument comprising tuned sonorous bodies, electromagnetsfor their actuation, and means for delivering properly timed electricpulsations to Said electromagnets; said electromagnets being dissonorousbodies, to a wire of relatively high resistance, for the lowest sonorousbodies.

9. A musical instrument comprismg magnetically attractive sonorousstrlngs, electromagnets to which said strings bear the relation ofarmatures, and means for delivering properly timed electric pulsationsto said electromagnets; the electromagnets actuating the upper sonorousstrings being wound to have a low resistance and being located closer totheir strings than the electro-' magnets, farther down the scale.

10. An electrical musical instrument comprising a sonorous body, anelectromagnet for its actuation, a rotary pulsation-pro ducing means, asource of current therefor, and means under the control of the operatorfor varying the amplitude of vibration of. said body by graduallyvarying the voltage of the current generated by said source.

11. An electrical musical instrument comprising, in combination,sonorous bodies and electromagnets for effecting their vibration; arotary pulsator; a motor for driving said pulsator; a source of electricenergy in circuit with the pulsator and electromagnets through branchcircuits; means operative at will for varying the voltage of the sourceof ing atwill the resistance of the branch circuits containing theelectromagnets.

12. A musical instrument comprising, in

combination a sonorous body; an electromagnet for its actuation; arotary makeand-break devlce; a source of electnc cur rent; means forconveying current from' of the generator.

14. A musical instrument comprising, in combination, sonorous bodies;electric means for their actuation; a generator supplying current tosaid means; a rotary circuit breaker for producing pulsations in saidcurrent; an exciter delivering current to the field windings of saidgenerator; and a pedal-controlled rheostat for varying the strength ofcurrent delivered by said exciter to said field.

15. A musicalinstrument comprising, in combination, a series of sonorousbodies; a source of electric energy a series of electromagnets directlyattracting 'and thus efiecting vibration of said bodies, one magnet foreach such body;.branch circuits each including a magnet of the seriesmeans for simultaneously introducing a separate resistance into thecircuit of each magnet; and means for completing the several magnetcircuits independently.

16. A musical instrument having strings difiering in size and length,electromagnets, and means for delivering electric pulsations thereto forthe actuation of said strings, the electromagnets actuating the largeand long strings being Wound with many windings of relatively fine wire,and the electromagnets actuating the finer and shorter strings beingwound with relatively heavy wire.

17. A musical instrument having strings difi ering in size and length; amagnet rail, and magnets carried thereby for the actuation of saidstrings, the magnets for the fine and shorter strings being wound withheavier wire than is used for the windings of the other magnets.

18. A musical instrument having strings differing in size and length, amagnet rail, electromagnets carried by said rail, and

means for delivering properly timed electric pulsations thereto, themagnets associated with the fine and short strings and also with thelong and heavy strings being located nearer to their strings than themagnets associated with the intermediate strings.

In testimony that we claim the foregoing invention, We have hereunto setout hands this 20th day of June, 1907.

MELVIN L. SEVERY. GEORGE B. SINCLAIR. Witnesses:

A. B. UPHAM,

CHARLES GARRISON.

